Buildkite checkout hook with retry (to mitigate "reference is not a tree" Git error)

checkout-retry.sh

#!/bin/bash
set -ex

if [ -d .git/ ]; then
	git remote set-url origin "$BUILDKITE_REPO"
else
	git clone "$BUILDKITE_REPO" .
fi

git clean -fdqx
git submodule foreach --recursive git clean -fdqx

if [ "$BUILDKITE_PULL_REQUEST" != false ]; then
  git fetch -v origin refs/pull/"$BUILDKITE_PULL_REQUEST"/head

  counter=1 limit=5;
  while ! git checkout -f "$BUILDKITE_COMMIT" && [ "$counter" -lt "$limit" ]; do
    sleep 5;
    git fetch -v origin refs/pull/"$BUILDKITE_PULL_REQUEST"/head
    counter="$(( counter+1 ))";
  done

  if [ $counter -eq $limit ]; then
    exit 1
  fi

elif [ "$BUILDKITE_COMMIT" = "HEAD" ]; then
  git fetch -v origin "$BUILDKITE_BRANCH"
  git checkout -f FETCH_HEAD
else
  git fetch -v origin "$BUILDKITE_COMMIT"
  git checkout -f "$BUILDKITE_COMMIT"
fi

git submodule sync --recursive
git submodule update --init --recursive --force
git submodule foreach --recursive git reset --hard

git clean -fdqx
git submodule foreach --recursive git clean -fdqx